Hypothermia and hyperthermia, which are conditions created by thermal disturbances, are caused when a body's core temperature lowers to such an extreme temperature that metabolic functions cannot occur, or more heat is absorbed or generated by the body than it can dissipate. Both thermal disturbances are common and can be life-threatening if not properly and quickly diagnosed and treated. The risk of hyperthermia, which can lead to heat exhaustion and heat stroke, is high among groups that participate in strenuous physical activities such as competitive athletics, and those that work outdoors when the temperature may be dangerously high, such as construction workers. Outdoors enthusiasts who spend a large amount of time in cold-weather climates, or those that participate in water sports, are prone to hypothermia. Heat and cold-related conditions are also common among military personnel who serve in extreme climate areas such as the desert and the arctic.
Although the brain is the organ that is most sensitive to temperature-induced damage, this damage is conventionally treated by raising or lowering body temperature by affecting the temperature of the entire body as opposed to the head, because it is conventionally understood that layers of insulation surrounding the brain make removing heat from or applying heat to the brain via the head is ineffective and slow. Conventional treatments include removing or adding additional clothing, placing the entire body or a portion thereof in a bath of cold or warm water, drinking cold or warm liquids, and resting or moving the body to increase or decrease body activity. Often individual body parts are cooled or heated using ice, an electric heating pad, or reusable packs filled with a thermally retentive substance such as polypropylene glycol gel, which may be heated, cooled, or frozen for both hot and cold applications. People affected by heatstroke are also placed in cooled or refrigerated areas. Likewise, people suffering from hypothermia are placed in warm or hot rooms.
Many significant drawbacks are associated with conventional methods of treating thermal-related conditions. Conventional methods and devices have severe limitations as they all work against the biology of the human body. In some cases, drawbacks accrue because of the mechanism of heating or cooling. Consider, for example, gel packs. The gel substance in a gel pack is generally encased within a very thin layer of plastic or other, similar material. This configuration allows for adequate thermal transfer or exchange either to or from the skin, but can also allow for excess thermal transfer or exchange with the environment, causing some of the heating or cooling capability of the gel pack to be lost to the environment, instead of being transferred to the part of the body to which it is being applied.
When the core temperature of the body is dangerously low, i.e., hypothermic, a conventional therapeutic treatment approach is to heat the entire body in the belief that the core temperature will be raised to a safe level. However, testing by Applicant indicates that heating the entire body may only result in raising the temperature of the body's extremities rather than the core temperature, and raising core temperature is the only effective way to treat hypothermia. By heating the body surface, the peripheral thermal receptors located in the extremities, send signals to the brain that the body is too hot, in which case the brain will respond by cooling the core temperature even more. Thus, the brain may negate the effects of a whole body thermal treatment and may even cause the person suffering from hypothermia to decrease core temperature further, even though his or her extremities seem to be warming.
On the other hand, if, for example, an athlete suffers hyperthermia as a result of too strenuous an activity, and the athlete's entire body is cooled or the skin of the body is cooled, the athlete's body runs a risk of fatally overheating as a result of activating thermal receptors which detect cooling. The brain reads the cool temperature of the skin surface as a signal that the body is too cold, causing the brain to activate mechanisms to deleteriously increase the core temperature.
A major drawback of conventional methods of changing body core temperature is the stimulation of thermal peripheral receptors on the skin. This stimulus sends a signal to the brain. If cold is applied, the signal will cause the brain to produce heat, which is the reason people shiver when exposed to cold; e.g., a cold wind, cold ambient temperature, cold water, etc. Shivering occurs as a result of the brain sending impulses for muscles to contract because muscle contraction generates heat. In addition to the production of heat, the brain sends a signal to the blood vessels on the surface of the body to contract, i.e., vasoconstriction. Vasoconstriction reduces heat loss and increases the internal or core temperature of the body. Muscle, heart, and vasculature all work at full force to generate heat when the peripheral skin receptors are activated, which is the reason a soldier or an athlete, for example, dies from heatstroke, despite immersion of their body in ice water. There are cases of over-heated athletes who perished once taken to a room with an air conditioner and a low temperature. The brain of the athletes responded to cold stimuli by having the body produce more heat, causing the death of a person who was already very hot because the brain was hot before coming into the air conditioned room, and after entering the air conditioned room, the brain, misreading skin sensor input, increased its temperature even further, leading to metabolic shutdown and death.
Thus, conventional approaches to raising body temperature can cause heatstroke to be a fatal condition in many cases, and is one of the most lethal conditions experienced by a human being given that conventional attempts to resolve the overheating condition causes a further increase of body internal temperature. A similar situation occurs with hypothermia, since during warming of the body the brain, which is already cold, will send signals for the body to counteract the effects of the heat being applied. In this situation, the brain instructs the body to promote peripheral vasodilation to release heat, to reduce or stop metabolic functions, and to reduce muscle activity to reduce production of heat. Thus, conventional approaches to warming a hypothermic person can further reduce the temperature of the brain, causing in many instances the demise of the person.
The inadvertent causing of death of conventionally treated patients is compounded by other factors. One such factor is that the body is covered by fat, the tissue with the lowest thermal conductivity, and which has a thermal conductivity similar to oak, where k=0.00004 Kcal/(s·N·C). Therefore, cooling or warming up the skin not only is ineffective as far as heat or cold being transmitted through the skin into the body because of the thermal insulation of fat, but also because the cooling or warming up of peripheral thermal receptors causes the brain to generate the opposite thermal response, as described above.
The brain is the organ most affected during thermal disturbances, i.e., heatstroke or hyperthermia, or hypothermia, with the extreme effect being death, so many attempts to cool or warm up the brain involve the cooling or warming up the head. The challenge of conventional techniques of warming the brain is compounded by the body surface being covered by fat. Therefore, attempts to cool or warm the head are also ineffective and equally dangerous as cooling and warming the whole body, limbs, or the body surface as described hereinabove, and can just as quickly lead to brain damage and death. Attempts to cool or warm up the brain are affected because of the presence of fat, and the stimulation of skin receptors on the head causes the brain to generate the opposite response, similar to the situation that occurs when trying to heat or cool the extremities, as described herein. Also similar to cooling or heating the entire body, a change in temperature of peripheral receptors on the face and head results in an opposite reaction of the brain. In fact, the brain overcompensates for the change in temperature of the peripheral receptors, which can cause damaging effects to the brain.
Damage to the brain caused by thermal disturbances can also occur in medical operating room environments. A patient undergoing surgery runs a risk of suffering from hypothermia if the operating room is not kept warm enough during the procedure. Maintaining a high environmental temperature in the operating room allows the patient's body to remain warm while the patient is under general anesthesia, and allows the patient's organs to remain warm even while exposed. However, in such a hot working environment, physicians and staff in the operating room are often uncomfortably warm and may suffer from hyperthermia because of the clothing typically worn in such environments, in addition to a risk of infection as pathogens grow in warm temperatures.
Several remedies to this difficulty have been previously presented. For example, one such proposed solution is to use a heating device to warm the patient's body, so that the operating room may be kept at a comfortably cool temperature for the surgeons and staff. Such an approach has been implemented using a disposable, electrically heated blanket to cover the patient's body. However, the blanket does not completely prevent the patient's body heat from escaping into the environment, and the patient's temperature still lowers. Similarly, it has been proposed that the patient's body be completely enveloped in a garment that circulates warmed fluid between a heat source and the body through a series of serpentine tubes. However, a blanket or garment designed to heat the patient's body may obstruct the regions that must be accessed by the surgeon to complete a surgery successfully. If the blanket or garment comprises an open front to give the surgeon easier access, then the patient's body may lose much needed thermal energy through the opening. An alternate solution is to cool surgeon and staff's bodies individually so that a warmer room temperature may be maintained. Such an approach can be obtained by a conventional cooling vest that can be worn by each surgeon or staff person, but the same issues as cooling skin surface occurs, in addition to infection risk in a warm environment, as described hereinabove.
Conventional treatments involving directly heating or cooling the brain have relied on invasive methods with injection of fluid. For example, medical professionals currently employ the technique of cooling the brains of patients who have suffered cardiac arrests to reduce the amount of oxygen the brain and heart need to keep working. The conventional approach to cooling the brain in this situation is by covering the patient's body with thermal transfer vests or blankets, configured to cool the body, or by injecting cold fluid into the patient's body. However, such approaches have been shown to be ineffective as patients tend to shiver intensely during the procedure, which equates to high heat production.
The challenges associated with methods for treating cardiac arrest patients, and for warming or cooling surgeons or patients in operating room environments using thermal energy, are similar to those discussed above related to thermal disturbance treatments. Warming or cooling the patient's entire body may cause peripheral or internal receptors to signal to the brain that it must overcompensate with an opposite change in brain temperature, resulting in hyperthermia or hypothermia. Moreover, in the case of cardiac arrest patients, the temperature of extremely cool fluid cannot be regulated, thus there is a risk that the cool fluid may result in excessive cooling of the body. Thus, conventional solutions to cooling the brain can result in unforeseen overcompensation and may cause thermal disturbances opposite to those that they are proposed to correct, thus exacerbating the very situation that was being corrected.
Controlling core brain temperature is also important in patients suffering from traumatic brain injury. However, the same limitations and drawbacks of conventional approaches to controlling core brain temperature described herein prevent a predictably successful outcome, and brain injury remains a common complication.